This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background: The timed-breeding program at the Tulane National Primate Research Center uses exogenous progesterone administration to control the time of ovulation. Methods: Human progesterone is administered by intramuscular injection at a dose of 5mg. The female is placed with the male 14 days after the last injection. Ultrasonography conducted 24 or 31 days after placing the female with the male confirms that pregnancy generally occurs 4 days after introduction to the male. This procedure allows for the efficient use of the males and provides a conception date+24 hours. Results/Discussion: In the spring/summer of 2008, 24 live births occurred as a result of time breeding efforts. These infants were assigned to either R. Veazey (AIDS research) or D. Phinney (gene therapy). For the 2008 breeding season, 15 females and 5 males are being used to provide infants to support a project of D. Phinney. Currently there are 2 confirmed pregnancies. The other females are awaiting ultrasounds and/or being placed with a male for breeding.